1. Field of the Invention
The present invention relates to electronic switches. More specifically, the present invention relates to using latching micro-magnetic switches to connect circuits, such as attenuators, capacitors, phase array antenna devices, or the like, to a circuit or signal path.
2. Background Art
Switches are typically electrically controlled two-state devices that open and close contacts to effect operation of devices in an electrical or optical circuit. Relays, for example, typically function as switches that activate or de-activate portions of electrical, optical or other devices. Relays are commonly used in many applications including telecommunications, radio frequency (RF) communications, portable electronics, consumer and industrial electronics, aerospace, and other systems. More recently, optical switches (also referred to as xe2x80x9coptical relaysxe2x80x9d or simply xe2x80x9crelaysxe2x80x9d herein) have been used to switch optical signals (such as those in optical communication systems) from one path to another.
Although the earliest relays were mechanical or solid-state devices, recent developments in micro-electro-mechanical systems (MEMS) technologies and microelectronics manufacturing have made micro-electrostatic and micro-magnetic relays possible. Such micro-magnetic relays typically include an electromagnet that energizes an armature to make or break an electrical contact. When the magnet is de-energized, a spring or other mechanical force typically restores the armature to a quiescent position. Such relays typically exhibit a number of marked disadvantages, however, in that they generally exhibit only a single stable output (i.e., the quiescent state) and they are not latching (i.e., they do not retain a constant output as power is removed from the relay). Moreover, the spring required by conventional micro-magnetic relays may degrade or break over time.
Non-latching micro-magnetic relays are known. The relay includes a permanent magnet and an electromagnet for generating a magnetic field that intermittently opposes the field generated by the permanent magnet. The relay must consume power in the electromagnet to maintain at least one of the output states. Moreover, the power required to generate the opposing field would be significant, thus making the relay less desirable for use in space, portable electronics, and other applications that demand low power consumption.
The basic elements of a latching micro-magnetic switch include a permanent magnet, a substrate, a coil, and a cantilever at least partially made of soft magnetic materials. In its optimal configuration, the permanent magnet produces a static magnetic field that is relatively perpendicular to the horizontal plane of the cantilever. However, the magnetic field lines produced by a permanent magnet with a typical regular shape (disk, square, etc.) are not necessarily perpendicular to a plane, especially at the edge of the magnet. Then, any horizontal component of the magnetic field due to the permanent magnet can either eliminate one of the bistable states, or greatly increase the current that is needed to switch the cantilever from one state to the other. Careful alignment of the permanent magnet relative to the cantilever so as to locate the cantilever in the right spot of the permanent magnet field (usually near the center) will permit bi-stability and minimize switching current. Nevertheless, high-volume production of the switch can become difficult and costly if the alignment error tolerance is small.
What is desired are bi-stable, latching relays or switches that do not require power to hold their states. Such a switch should be reliable, simple in design, low-cost and easy to manufacture, and should be useful in optical and/or electrical environments.
A method and apparatus for controlling the coupling of a first circuit into another circuit or signal path is described. A micro-machined latching switch (i.e., relay) of the present invention can be switched between two states. In a first state, the switch couples the first circuit into a signal path. In a second state, the switch provides a conductive path that bypasses the first circuit.
In an aspect of the present invention, a moveable element is supported by a substrate and has a magnetic material and a long axis. At least one magnet produces a first magnetic field. The first magnetic field induces a magnetization in the magnetic material. The magnetization is characterized by a magnetization vector pointing in a direction along the long axis of the moveable element. The first magnetic field is approximately perpendicular to a major central portion of the long axis. A coil produces a second magnetic field to switch the moveable element between first and second stable states. Temporary application of the second magnetic field is required to change direction of the magnetization vector, which causes the moveable element to switch between the first and second stable states. In the first stable state, the moveable element does not couple the first circuit in series with a signal. In the second stable state, the moveable element couples the first circuit in series with the signal.
The first circuit can include any number of components and component configurations. In an aspect, the first circuit is an attenuator circuit, such as a resistive attenuator circuit. In another aspect, the first circuit is a capacitive circuit. In another aspect, the first circuit is a filter circuit. In further aspects, the first circuit can be other circuit types.
In aspects of the present invention, the moveable element can include one, two, three, or more electrically conductive portions.
In one aspect, the moveable element includes first and second electrically conductive portions. In a first stable state, the first electrically conductive portion forms an electrically conductive path (e.g., a short circuit) in series with the signal. In the second stable state, the second electrically conductive portion couples a first signal line of the signal to the circuit.
In another aspect, the moveable element comprises first, second, and third electrically conductive portions. In the first stable state, the first electrically conductive portion forms an electrically conductive path in series with the signal. In the second stable state, the second electrically conductive portion couples a first signal line of the signal to an input to the circuit, and the third electrically conductive portion couples a second signal line of the signal to an output of the circuit.
In another aspect, a pair of moveable elements are used to couple the circuit into the signal path. A first signal line of the signal path is coupled to the first moveable element, and a second signal line of the signal path is coupled to the second moveable element. In the first stable state, the pair of moveable elements are electrically coupled together. Thus, in the first stable state, the circuit is not coupled into the signal path. In the second stable state, the circuit is coupled into the signal path between the moveable elements.
The latching micro-magnetic switch of the present invention can be used in a plethora of products including household and industrial appliances, consumer electronics, military hardware, medical devices and vehicles of all types, just to name a few broad categories of goods. The latching micro-magnetic switch of the present invention has the advantages of compactness, simplicity of fabrication, and has good performance at high frequencies.
These and other objects, advantages and features will become readily apparent in view of the following detailed description of the invention.